Pest profile

American Plum Borer

Euzophera semifuneralis · Lepidoptera: Pyralidae[2]

American plum borer larvae feed in the cambium around branch crotches and the lower trunk, but they can only get in through fresh bark wounds.[1]

American plum borer moth, a gray moth with brown and black wing markings, resting on a pale surface
American plum borer moth, a gray moth with brown and black wing markings, resting on a pale surface. Photo: Trix Niernberger, public domain (CC0), via iNaturalist

How to identify it

  • Adults are gray moths with brown and black wing markings; larvae are dull green, pinkish or white; both are up to about 1 inch.[1]
  • Signs are heavy gumming, reddish-orange frass and webbing at crotches, the lower trunk and the root crown.[1]

Look-alikes

Look-alikeHow to tell them apart
Clearwing borersClearwing moths, flatheaded borers and shothole borers share hosts; check larval proleg hooks with a hand lens before acting.[1]

Where it lives

It occasionally bores in fruit and nut trees, mountain ash, olive and sycamore, mostly young trees.[1]

US map: public records from 36 states since 1990 (GBIF).

Biology and life cycle

Moths emerge from about April and lay eggs in bark wounds; larvae enter the wound at once.[1]

Mature larvae overwinter in cocoons within the tree, and there are three to four generations a year.[1]

Damage and signs

  • Feeding weakens limbs, which often break in wind, and sometimes kills young trees.[1]

Health risk

It lives under bark; UC IPM mentions no risk to people.[1]

Control

Prevention

Avoid bark wounds from pruning, sunburn and string trimmers; whitewash young trunks with interior latex diluted with equal water.[1]

When to call a professional

Where damage is present, a trunk spray from the main crotch to the soil line usually needs a professional applicator.[1]

Common questions

What is the orange sawdust and gum at my tree's crotch?
American plum borer larvae cause gumming and reddish-orange frass at crotches and the lower trunk.[1]
How do I prevent it?
Protect bark from wounds, since larvae can enter only through fresh injuries.[1]

Sources

  1. University of California Statewide IPM Program, “American Plum Borer (Pests in Gardens and Landscapes).” ipm.ucanr.edu/PMG/GARDEN/FRUIT/PESTS/amerplumbor.html (accessed 2026-10-06)
  2. iNaturalist, “Euzophera semifuneralis taxon page (order and family).” www.inaturalist.org/taxa/220023 (accessed 2026-10-06)

Updated 2026-10-14. Built from sourced records. Spot an error? Tell us.